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我在Swift Playground中执行了下面的代码。我预计“第一秒”计数为5,“秒”计为10,因为两者的起点都相同。但是结果都是5。我在这里错过了什么吗?从固定的开始时间计算不同时间点的经过时间
let startDt = NSDate()
sleep(5)
let endDt = NSDate()
let calendar = NSCalendar.currentCalendar()
let datecomponenets = calendar.components([NSCalendarUnit.Second] , fromDate: startDt, toDate: endDt, options: [])
let seconds = datecomponenets.second
print("First Seconds: \(seconds)")
sleep(5)
let endDt1 = NSDate()
let calendar1 = NSCalendar.currentCalendar()
let datecomponenets1 = calendar.components([NSCalendarUnit.Second] , fromDate: startDt, toDate: endDt1, options: [])
let seconds1 = datecomponenets.second
print("Second Seconds: \(seconds1)")